Switch over to the google3 unix_file File*.

I also moved macros.h to base/macros.h to ease google3 porting, at
the expense of a larger than necessary change. (I learned my lesson,
though, and didn't make the equivalent base/logging.h change.)

I'm not sure whether we want to keep the unix_file MappedFile given
our existing MemMap, but it's easier to bring it over and then remove
it (and possibly revert the removal) than to bring it over later.

Change-Id: Id50a66faa5ab17b9bc936cc9043dbc26f791f0ca
diff --git a/src/runtime_linux.cc b/src/runtime_linux.cc
index 72989a6..e2050d1 100644
--- a/src/runtime_linux.cc
+++ b/src/runtime_linux.cc
@@ -34,7 +34,7 @@
   }
 };
 
-struct OS {
+struct OsInfo {
   void Dump(std::ostream& os) {
     utsname info;
     uname(&info);
@@ -242,7 +242,7 @@
   bool has_address = (signal_number == SIGILL || signal_number == SIGBUS ||
                       signal_number == SIGFPE || signal_number == SIGSEGV);
 
-  OS os_info;
+  OsInfo os_info;
   const char* cmd_line = GetCmdLine();
   if (cmd_line == NULL) {
     cmd_line = "<unset>"; // Because no-one called InitLogging.
@@ -258,7 +258,7 @@
                                       info->si_code,
                                       GetSignalCodeName(signal_number, info->si_code))
                       << (has_address ? StringPrintf(" fault addr %p", info->si_addr) : "") << "\n"
-                      << "OS: " << Dumpable<OS>(os_info) << "\n"
+                      << "OS: " << Dumpable<OsInfo>(os_info) << "\n"
                       << "Cmdline: " << cmd_line << "\n"
                       << "Thread: " << tid << " \"" << thread_name << "\"\n"
                       << "Registers:\n" << Dumpable<UContext>(thread_context) << "\n"